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Decimals and Roman Numerals

Date: 10/22/98 at 03:21:16
From: Richard Collecutt
Subject: Roman numerals

Do you know of any method for representing Roman numerals in a 
floating point format? For example, does 10.5 = X.V?

Date: 10/22/98 at 08:26:37
From: Doctor Rick
Subject: Re: Roman numerals

Hello, Richard. 

The Romans didn't have a standard way of writing fractions (or decimals.)  
Usually, they just wrote out the appropriate word, such as "tres septimae" 
for three-sevenths.

When they needed to do serious calculations with fractions, the Romans 
used the uncia, a unit that meant 1/12 of anything.  There were names and 
symbols for different multiples of the uncia.  For example, six unciae, 
or 6/12, made up the semis.  The semis meant one-half, and its symbol 
was an S cut in half (this looks a lot like a backward 2.)  Unfortunately, 
uncia symbols didn't follow any real system, and they were never entirely 

Jeff Miller's page on the "Earliest Uses of Symbols for Fractions and 
Decimals" has more information about the uncia:   

It's important also to understand that Roman numerals are not a place-
value system; there is no ones place, tens place, etc., so there is 
no "place" for a decimal point. If I were to invent a system for 
writing fractional quantities in Roman numerals, other than writing a 
fraction with Roman numerals in the numerator and denominator, I would 
take a cue from the method, occasionally seen, of writing a horizontal 
bar over a Roman numeral to signify multiplication by 1000:
  M = 1000 * 1000 = 1,000,000

and use, say, a bar under a Roman numeral to signify division by 1000. 

- Doctors Rick and Ursula, The Math Forum   
Associated Topics:
Elementary Math History/Biography
Elementary Number Sense/About Numbers
High School History/Biography
Middle School History/Biography
Middle School Number Sense/About Numbers

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